Systemd Networkd MAC Address generation for VLAN Interfaces

systemd

I'm creating a VLAN interface with networkd like this on a bunch of servers with equal config:

[NetDev]
Name=vlan3
Kind=vlan

[VLAN]
Id=3

Then I'm creating an interface like this with it:

[Match]
Name=vlan3

[Network]
Address=10.1.0.x/24

Where x is a unique number for every server.

My problem is that the VLAN is not really usable as networkd seems to choose the same MAC address (in my case 72:ae:43:d7:0f:d7) on every server.
I know I can set a MAC address using MACAddress or influence the generation via MACAddressPolicy. But what is networkd without specifying either?

Best Answer

The default MACAddress for a [NetDev] section is defined in the official documentation:

The MAC address to use for the device. If none is given, one is generated based on the interface name and the machine-id(5).

If all your machines have the same MAC Address being generated, it's because they have the same machine-id. Refer to the linked official docs on machine-id on how you can influence that.

Related Solutions

Systemd-networkd and direct routes

So the solution here is a bit tricky: you need to add gateway as a pointopoint parameter with /32 mask. This works:

[Match]
Name=enp0s3

[Address]
Address=192.168.0.2
Peer=192.168.0.1/32

[Network]
Gateway=192.168.0.1

Can’t get systemd-networkd to start successfully

It exits with 226/NAMESPACE, which usually means that it was unable to enter a namespace to enable the protection specified in the .service file.

There are at least two ways to solve it.

The easy and less secure way.

Copy /usr/lib/systemd/system/systemd-networkd.service to /etc/systemd/system/, open the copy with your favorite editor and remove the lines that start with Protect. This disables the sandboxing, and should let it start.

More advanced but more secure

Recompile the kernel with CONFIG_NAMESPACES=y.